1. Field of the Invention
The invention relates to a biologically degradable molding based on a starch-containing composite material and having at least two mold elements connected to one another by at least one connection element.
2. Description of the Related Art
U.S. Pat. No. 5,843,544 discloses a molding manufactured with the use of a starch-containing mixture. Said molding is provided with a hinge, wherein the hinge consists of a starch-containing cellular matrix. According to the teaching of U.S. Pat. No. 5,843,544 the hinge must comprise at least one notch or one fold in the hinge area, in order to permit a turning down or flexing of the hinge along the notch or the fold.
The hinge according to U.S. Pat. No. 5,843,544 exhibits, because of the notch or the fold, a reduced thickness in this area of the hinge, in order to reduce the stresses occurring on the inside of the hinge during the turning down or flexing.
It is disadvantageous, however, that said hinge breaks or tears easily along the notch provided or the fold.
In order to counteract this problem, according to the teaching of U.S. Pat. No. 5,843,544 a polyol-containing plasticiser such as glycerol, polyethylene glycol, propylene glycol or polypropylene glycol is applied to the hinge area.
The hinge known from U.S. Pat. No. 5,843,544 therefore has several disadvantages. First of all, the construction of the hinge with one or more notches or one or more folds is cumbersome. In particular, in the manufacture of large quantities of such hinges, such as are involved for example in the case of one-trip containers such as starch-based hamburger cases, it is difficult to manufacture such cumbersomely formed hinges with a high throughput. According to the teaching of U.S. Pat. No. 5,843,544 the baking mold is in the area in which the hinge area is baked preferably provided with a material with lesser heat capacity or with a poorer heat transfer power. Baking molds of this kind are difficult to manufacture and fault-prone in permanent operation.
It is also disadvantageous that there have to be applied to the hinges known from U.S. Pat. No. 5,843,544 in a further processing step polyol-containing plasticisers, in order to be able to ensure adequate stability of the hinge. Said additional processing step is cumbersome and requires additional equipment. This makes it more expensive, for example, to manufacture mass-produced articles such as hamburger cases, which however have to be produced cheaply in order to be able to compete with the conventional hamburger cases based on polystyrene.
The object of the present invention is therefore to produce biologically degradable moldings which prevent the disadvantages known in the prior art and comprise a connection element which is simple to manufacture and possesses high flexibility.
The object on which the invention is based is achieved by the production of a biologically degradable molding based on a starch-containing composite material and having at least two mold elements connected to one another by at least one connection element, wherein the connection element extends substantially two-dimensionally and is connected at each of two mutually opposite end areas to a mold element, wherein the connection element comprises a first outer surface and a second outer surface, is manufactured from a starch-containing and flexible composite material and is free of notch- or fold-type depressions or cutouts.